164 MEDICINAL AND POISONOUS PLANTS 



arabiii into a kind of glucose sugar known as arabinose. A 

 similar sul)stance yielding arabinose forms about half of 

 gum tragacantli, about one-third of the gum being a carbo- 

 hydrate called tragacanthin (CoHioOj) which differs from 

 arabin in Ijeing insoluble, although it al^sorbs water and 

 swells exceedingly. Tragacanth is an exudation from wounds 

 made in the stems of the guni-l)earing tragacanth shrul) 



W •'^ % ') 





1 / 







'***Ta. 



. 156. — Gunj .Vraljic Trfc {Acacia Srncjal, Pulse Family, Ltyuiuinusa'). 

 A, flowering branch. B, flower. C, pod, half, allowing seeds. D, yeed, 

 cut between the seed-leaves to show seed-stem and seed-l^ud. E, seed, 

 cut across. (Taubert.) — A tree aliout fi ni. tall; liark gray; leaves 

 grayish; flowers yellow; pod yellowish. Native homo, tropical ,\frira. 

 This tree yields the best gum; several other species produce an inferior 

 tiuality. 



(Fig. 157) and related species. The root of the marshmallow 

 (Fig. 158) contains about one-third of its weight of a mucilage, 

 having the same formula as tragacanthin. The same formula 

 is given also to the mucilage yieldetl copiously by the outer 

 coat of the flaxseed (Fig. 279). A similar mucilage but with 

 the formula C,sH.;„<>ii is obtained in large quantities from 

 the outer coat of quince seed (Fig. 9o). The slipperiness of 



